add_2 function and its test

core.py

@@ -1,3 +1,7 @@
 def add(x, y, z=0):
     """Add two (or three) objects"""
-    return x + y + z
+    return x + y + z
+
+def add_2(x):
+    """Add two to a number"""
+    return x + 2

test_core.py

@@ -1,13 +1,19 @@
-from core import add
+from core import *
 
 
 def test_add():
     """Check that `add()` works as expected"""
-    
+
     assert add(2, 3) == 5
 
 
 def test_add_z():
     """Check that `add()` works as expected"""
-    
+
     assert add(2, 3, 1) == 6
+
+
+def test_add_2():
+    """Check that `add()` works as expected"""
+
+    assert add_2(3) == 5